flywheel weight


7 replies to this topic
  • KAMMP

Posted August 23, 2009 - 12:14 PM

#1

Curious what the popular opinion is regarding a heavier flywheel or mx. I have an 06 450 and only ride mx. I know everybody loves them for woods riding but would really like to hear what people who ride mx have to say about a heavier flywheel. thanks

  • grayracer513

Posted August 23, 2009 - 02:05 PM

#2

IMO, the bike should have been built with the GYT-R off-road flywheel (+9oz). It does everything better with it.

  • Ray450

Posted August 24, 2009 - 05:42 AM

#3

I have put flywheel weights on about half the bikes I have raced in the last 15 or so years. Typically, I use the heaviest available, or I just can't feel anything. For me, it's more about the ability to lug down lower than it is trying to chase tractable power. I had a weight on my 03 YZ 450 (many bikes ago), I even had a weight on my KTM SX450 (stall master, thank god it had a button, but most of it's stalls were carb related flameouts which a weight doesn't help as much with), but never felt like I needed one on my RMZ 450. I also rarely ran them on any of my 250 2 strokes, but did on my 500s (KX and Cr). I only have a few hours on my 09 YZ450F, but I'm fairly sure I'll be getting the heavy offroad weight for it. It's fine stock on a M/X track, but is easier to stall offroad when the revs are low in nasty/tight/or endurocross type sections. If I only used it for M/X, I probably wouldn't bother. I also race vintage on a 82 CR480R, a bike thats pretty easy to stall and wasn't made with enough flywheel weight. There hasn't been a weight available for a long time, so I just made my own. I made my own spacer by turning down a spare cover. I made it 1 pound (15.5 ounces before welding her on), trying to carry as much of the weight towards the outside to increase inertia without adding lots of weight. I thought I might be going overbored, and figured it would be easier to lighten later. It works great, and if anything, I wish I had started off a bit heavier now. As much torque and power as these 450s make, I just can't see how most riders can realy feel the very light flywheel weights. I also put the heaviest weight Steahly made for a YZ 125 on my daughters bike. She raced offroad. Steahly actually tried talking me out of it and using a lighter one. I was amazed how well it worked though, you could almost come to a complete stop before the engine would die. And I was surprised to find that it really didn't seem to give up anything in a drag race. We sold that bike to another girl racer later who kept it for years (I had also lowered the subframe, cut the seat down, softened up the suspension, stabilizer, jetted for offroad and customized it for a smaller offroad rider). She told me she couldn't sell it because she was never able to try anyone else's bike that worked anywhere near as well. I think it had more to do with that weight than any of the other mods.

  • cowboyona426

Posted August 24, 2009 - 10:08 AM

#4

x2 on the GYT-R heavy off-road flywheel.

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  • eddie06450

Posted August 24, 2009 - 04:38 PM

#5

I have a ? about them as well the bike is built and sent from the factory all balanced and when you put a flywheel weight on weather its a add on or the full replacement what does this do to the balance of the motor it may make it more rider friendly but what is this doing to the bottom end bearings and all? ALL INPUT is very well respected. THANKS

  • rexbond007

Posted August 24, 2009 - 04:48 PM

#6

I have a ? about them as well the bike is built and sent from the factory all balanced and when you put a flywheel weight on weather its a add on or the full replacement what does this do to the balance of the motor it may make it more rider friendly but what is this doing to the bottom end bearings and all? ALL INPUT is very well respected. THANKS


you have a point, does a flywheel weight shorten a life of a motor and why are they not doing this from factory?

  • grayracer513

Posted August 24, 2009 - 05:41 PM

#7

I have a ? about them as well the bike is built and sent from the factory all balanced and when you put a flywheel weight on weather its a add on or the full replacement what does this do to the balance of the motor it may make it more rider friendly but what is this doing to the bottom end bearings and all? ALL INPUT is very well respected. THANKS

If the flywheel or weight itself is balanced (all of the welded weight flywheels I'm aware of are carefully rebalanced after installation), and they run straight, they do nothing at all to the balance of the engine. There is no need to re-balance.

you have a point, does a flywheel weight shorten a life of a motor and why are they not doing this from factory?

The factory is doing whatever they can to enhance high RPM performance and quick acceleration from a theoretical standpoint. Light flywheels contribute to this goal. The practical reality often varies from engineering theory, and at least in some applications, reversing this trend actually improves performance.

It has no effect on engine longevity, and the only strain it places on the engine is against the left crank axle, which handles the effect of the increased rotational inertia.

Note that Falicon adds weight to their stroker cranks because the base YZF crank is so light.

  • Jibba

Posted August 25, 2009 - 12:33 AM

#8

Dont you think that if a heavier FW would damage the engine or reduce longevity, then Yamaha would not offer GYTR FW's?

My 2 cents worth.





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